Process for producing acetaldehyde



United States Patent 3,381,037 PRGCESS FOR PRODUCING ACETALDEHYDETsutomu Ohmae, ()saka, Keizo Matsushiro, Ashiya-shi,

and Hiroshi Yamarnoto, Nishinomiya-slii, Japan, assignors to NipponGosei Kagaku Kogyo Kabushiki Kaisha, Osaka, Japan, a corporation ofJapan No Drawing. Continuation-in-part of application Ser. No. 240,129,Nov. 26, 1962. This application Jan. 14, 1966, Ser. No. 520,643

Claims priority, application Japan, Feb. 26, 1962,

Claims. ci. 260-604) This is a continuation-in-part of application Ser.No. 240,129 filed Nov. 26, 1962, now abandoned.

The invention relates to a process for producing acetaldehyde, moreparticularly a process for producing acetaldehyde by reacting ethylenewith oxygen and an aliphatic alcohol having carbon atoms up to 4 in thepresence of a catalyst.

Acetaldehyde is a well-known intermediate in the preparation of varioususeful organic compounds, and it is hitherto produced commercially byhydrating acetylene.

Recently, however, it was found by Dr. J. Smidt to be able to prepareacetaldehyde by contacting ethylene, oxygen and an aqueous solutioncontaining catalyst. In such process, water is used as not only reactionmedium but also one of the starting materials for the reaction. The useof large amount of water is necessary to proceed the reaction, whereasonly small amounts of watermiscible organic solvents may be used toincrease the solubility of the gases to the aqueous solution.

Unexpectedly, we have discovered that acetaldehyde may be also preparedwith desirably increased reaction rate by contacting ethylene, oxygenand an alcoholic solution containing a catalyst as describedhereinafter. The process can be clearly distinguished from the priorprocess as described above in point of employing substantially anhydrouslower aliphatic alcohols.

An object of the present invention is to provide a new process forproducing acetaldehyde.

A particular object of the present invention is to provide a process forproducing acetaldehyde from ethylene with increased reaction rate.

Said objects may be attained according to the process of the presentinvention by reacting ethylene, oxygen and an aliphatic alcohol havingcarbon atoms up to 4 under the conditions described hereinafter andrecovering acetaldehyde from the reaction mixture.

The precise mechanism by which the alcohols are preferably employed forthe reaction is not fully understood.

It is, however, suggested that the reaction carried out in the presentinvention may be represented by the following equations, because theremay be found the formation of acetaldehyde-dialkylacetal and water withacetaldehyde in the reaction mixture:

Catalyst CzHit2R0H+%o CH3CH(OR)z+HzO Catalyst oincutoRm-l-no CH3CHO+2ROHSaid acetal and water contained in the reaction mixture may furthermoreconvert into acetaldehyde according to the latter equation describedabove during distillation of the reaction mixture.

The preferred examples of the aliphatic alcohols employed in the presentinvention are methanol, ethanol, normal propanol, isopropanol, normalbutanol, isobutanol, secondary butanol and tertiary butanol. They arepreferably employed in substantially anhydrous form, The catalystemployed in the present invention consists of a palladium salt and atleast one of salts of metals selected from the group consisting ofcopper and iron. The salts may be preferably halides such as chlorideand bromide or carboxylates such as acetate, propionate and butyrate.Oxygen may be employed either in pure state or in diluted state such asair. The reaction may be preferably carried out at a temperature of fromabout 50 C. to 150 C., desirably from 60 C. to 100 C., and undersuper-atmospheric pressure up to about 100 atmospheres, desirably from10 to 50 atmospheres. The feed ratio of ethylene and oxygen may betheoretically 2:1 by mole, but from the point of practical view the useof the large excess of ethylene is preferred to avoid any explosiveaccident. The catalyst may be preferably used in the ratio of less thanabout 0.005 mole of a palladium salt and less than about 0.2 mole of acopper or iron salt or mixture thereof to 1 mole of an alcohol.

In carrying out the process of the present invention, a substantiallyanhydrous alcohol and the catalyst are charged and then ethylene andoxygen are introduced into a reaction zone wherein acetaldehyde isproduced. If necessary, they are occasionally or continuously charged.In another case, a gaseous mixture of ethylene, oxygen and vaporizedalcohol is passed over the catalyst supported on a suitable carrier.Acetaldehyde may be recovered from the reaction mixture by means offlash distillation or fractionation.

According to the present invention, acetaldehyde may be produced fromethylene with commercial advantages obtained by the further increasedreaction rate and more weak corrosion properties of the reaction mixtureto employed reaction vessel, pipes, valves, etc., compared with that inthe previous process described above carried out in an aqueous system.

The present invention is illustrated in detail by the followingexamples, In each example, an autoclave of one litre capacity, which waslined with titanium metal and was provided with an electromagneticstirrer, was employed as a reactor.

EXAMPLE 1 Into the autoclave, 250 g. of absolute ethanol, 1.5 g. ofpalladium chloride and 33.6 g. of cupric chloride were charged, and wereheated with agitation to maintain at a temperature of about C. duringreaction for about 4 hours. Ethylene and oxygen were introduced in molarratio of 6 to 1 into said autoclave up to about 45 atms., and they wereadditionally charged at every time when the fall of about 10 atms. inpressure was resulted. After the reaction was completed, it was shown bymeans of chemical analysis that the resulting mixture contained 60.1 g.of acetaldehyde and 93.9 g. of diethylacetal thereof. In practice,however, 88.7 g. of the former and 16.9 g. of the latter were recoveredby distillation of the mixture.

On the other hand, in the control prepared in the same way as describedabove except that 250 g. of water was used in place of ethanol, theyield of acetaldehyde was 26.0 g.

EXAMPLE 2 The procedure of Example 1 was repeated with the exceptionthat 0.75 g. of palladium chloride, 16.8 g. of cupric chloride and 25.0g. of cupric acetate monohydrate were employed as catalyst and thereaction was carried out under a pressure of about 10 atms. for 12 hoursand 40 minutes. After the reaction was complete, the resulting mixturewas distilled and 74.5 g. of acetaldehyde was obtained.

In the control prepared in the same way as described above except that250 g. of water was employed in place of ethanol, the yield ofacetaldehyde was 21.5 g.

EXAMPLES 3 TO 4 In each case, the procedure of Example 1 was repeatedwith the exception that anhydrous methanol or anhydrous tertiary butanolwas employed in place of ethanol. Results are shown in the followingTable I.

TABLE I Example No 3 4 5 Methanol (g.) 250 Tertiary Butanol (g.). r 250.Reaction Time 4 hrs 3 hrs. and 40 min. Products:

Acetaldehyde (g.) 100.3 52.5.

Acctal (g.) 10.1 1O

EXAMPLES 5 TO 6 In each case, the procedure of Example 1 was repeatedwith the exception that ferric chloride or ferric chloride 15 and cupricchloride in place of cupric chloride alone. Results are shown in thefollowing Table II.

What We claim is: 1. A process for producing acetaldehyde whichcomprises reacting at least 2 moles of ethylene with at least '1 mole ofoxygen and at least 4 moles of a substantially anhydrous alkanol havingless than 5 carbon atoms in the presence of a catalyst consisting of apalladium salt and at least one salt of a metal selected from the groupconsisting of copper and iron, said salts being selected from the groupconsisting of halides and alkanoates having from 2 through 4 carbonatoms and said catalyst being in a ratio of less than 0.005 mole of saidpalladium salt and less than 0.2 mole of said metal salt per mole ofalkanol and recovering acetaldehyde produced in the reaction mixture bydistillation.

2. A process as claimed in claim 1, wherein the alcohol is methanol.

3. A process as claimed in claim 1, wherein the alcohol is ethanol.

4. A process as claimed in claim 1, wherein the catalyst consists ofpalladium chloride and cupric chloride.

5. A process as claimed in claim 1, wherein the reaction is carried outat a temperature of from 50 C. to 150 C. and a superatmospheric pressureup to 100 atmospheres,

References Cited UNITED STATES PATENTS 3,076,032 1/ 1963 Riemenschneideret a1. 260604

1. A PROCESS FOR PRODUCING ACETALDEHYDE WHICH COMPRISES REACTING ATLEAST 2 MOLES OF ETHYLENE WITH AT LEAST 1 MOLE OF OXYGEN AND AT LEAST 4MOLES OF A SUBSTANTIALLY ANHYDROUS ALKANOL HAVING LESS THAN 5 CARBONATOMS IN THE PRESENCE OF A CATALYST CONSISTING OF PALLADIUM SALT AND ATLEAST ONE SALT OF A METAL SELECTED FROM THE GROU CONSISTING OF COPPERAND IRON, SAID SALTS BEING SELECTED FROM THE GROUP CONSISTING OF HALIDESAND ALKANOATES HAVING FROM 2 THROUGH 4 CARBON ATOMS AND SAID CATALYSTBEING IN A RATIO OF LELSS THAN 0.00K MOLE OF SAID PALLADIUM SALT ANDLESS THAN 0.2 MOLE OF SAID METAL SALT PER MOLE OF ALKANOL AND RECOVERINGACETALDEHYDE PRODUCED IN THE REACTION MIXTURE BY DISTILLATION.